Does touchpads have buttons?

Simon Thum simon.thum at
Mon Sep 29 06:25:26 PDT 2008

Søren Hauberg wrote:
> This stuff seems to only be in git. It's not in any releases, right?
Yes. It needs a current server also.

> The information I seem to get from the kernel is (BTN_TOUCH, 1) when
> the stylus is pressed to the screen, and (BTN_TOUCH, 0) when the
> stylus is removed. When I move the stylus around (when its pressed
> onto the screen), I don't get any BTN_TOUCH's.
Then you don't need any hysteresis :) I'd guess the HW does that 
internally then.

If you're curious anyway, from wikipedia: Hysteresis represents states, 
and the characteristic curve shape is sometimes remiscent of a two-value 
state, also called a bistable state. The hysteresis curve really 
contains infinitely many states, but a simple application is to let the 
threshold regions (usually to the left and to the right) represent 
respectively the on and off states. In this way, the system can be 
regarded as bistable.

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